The present invention relates to electrical receptacles incorporating circuit elements for protecting components of electrical apparatus connected to such receptacles against damage due to high, transient voltages in the electrical circuit wherein the receptacle is incorporated. More specifically, the invention relates to wall mount electrical receptacles having unique structural features particularly directed to efficient incorporation of integral means for clamping high, transient voltages to a lower, safe level.
Electrical receptacles having integral surge suppressors operative for protecting electrical apparatus connected to the outlets from transient line voltage surges have been provided both in so-called power strips which themselves are plugged into a standard wall receptacle, and in otherwise conventional receptacles flush-mounted with a room wall in a standard junction box. An example of the former is found in U.S. Pat. No. 4,259,705 which discloses a housing having several sets of plug-receiving openings for connection thereto of one or more electrical appliances or other apparatus, as well as a cord terminating in a plug for for connection to an AC power source through a standard receptacle. The housing contains circuit means connected to the line, neutral and ground contacts of each set of receptacle openings to provide protection against voltage surges across the line and neutral, line and ground, and neutral and ground lines. Another form of surge-protection device having a single set of plug-receiving openings and corresponding set of blades for insertion in a standard receptacle, and further including a light-emitting diode for indicating the operative condition of the protective circuitry, is shown in U.S. Pat. No. 4,089,032.
The wall mounted receptacle of U.S. Pat. No. 4,217,619 is modified from a duplex receptacle to provide a single set of plug-receiving openings and contacts with a single surge protection device (varistor) positioned in the space normally occupied by the second set of contacts. More recent U.S. Pat. No. 4,688,135 discloses a duplex, wall mounted receptacle having surge-suppressing components mounted in a module connected to the receptacle by separate plug-in means.
Due to the proliferation of electrical or electronic devices requiring protection from high transient voltages on AC power lines, it is desireable to have available wiring devices such as flush-mounted wall receptacles with built-in surge suppression means. It is further desireable that such receptacles be of the same size as previous, standard receptacles having no surge suppression capability, and include means for mounting in conventional trade or junction boxes. As a still further desireable feature, such receptacles should be available in so-called "hospital grade" form, this designation being applied by testing organizations to wiring devices of exceptionally rugged and high quality design.
The present invention is directed to, and includes among its objects, the provision of electrical receptacles having some or all of the foregoing features. That is, the invention contemplates provision of a hospital-grade, flush-mounted wall receptacle of standard size and external configuration including compact and efficiently mounted components for protecting electrical devices connected to the receptacle against damage due to voltage surges or spikes on the AC circuit to which the receptacle is connected. In another aspect, the invention is concerned with novel and improved mounting means, including a mounting strap positioned entirely exteriorly of the housing, for a hospital-grade, flush-mounted wall receptacle. The mounting means includes cooperative portions on the mounting strap and housing which maintain the receptacle in assembled relation without the usual screws, rivets or other such fastening means.